摘要：大家好，我是小舒，今天和大家一起探讨一下编程的规范，不管是全新的工程，还是老工程的维护，规范的编程可以赏心悦目，不仅愉悦自己也能愉悦他人，更能提升工作的效率。之前和大家分享过很多关于编程的文章，今天来分享一下老外的编程风格。
大家好，我是小舒，今天和大家一起探讨一下编程的规范，不管是全新的工程，还是老工程的维护，规范的编程可以赏心悦目，不仅愉悦自己也能愉悦他人，更能提升工作的效率。之前和大家分享过很多关于编程的文章，今天来分享一下老外的编程风格。
编写代码时最重要的一条规则是：检查周围的代码并尝试模仿它。
作为维护人员，如果收到的补丁明显与周围代码的编码风格不同，这是令人沮丧的。这是不尊重人的，就像某人穿着泥泞的鞋子走进一间一尘不染的房子。
因此，无论本文推荐的是什么，如果已经编写了代码并且您正在对其进行修补，请保持其当前的样式一致，即使它不是您最喜欢的样式。
这里列出了最明显和最重要的一般规则。在你继续阅读其他章节之前，请仔细检查它们。
使用C99标准不使用制表符，而是使用空格每个缩进级别使用4个空格在关键字和左括号之间使用一个空格在函数名和左括号之间不要使用空格int32_t a = sum(4, 3); /* OK */int32_t a = sum (4, 3); /* Wrong */不要在变量/函数/宏/类型中使用_或前缀。这是为C语言本身保留的对于严格的模块私有函数，使用prv_ name前缀对于包含下划线_ char的变量/函数/宏/类型，只能使用小写字母左花括号总是与关键字(for, while, do, switch, if，…)在同一行size_t i;for (i = 0; i 在比较操作符和赋值操作符之前和之后使用单个空格int32_t a;a = 3 + 4; /* OK */for (a = 0; a 每个逗号后用单空格func_name(5, 4); /* OK */func_name(4,3); /* Wrong */不要初始化静态和全局变量为0(或NULL)，让编译器为您做static int32_t a; /* OK */static int32_t b = 4; /* OK */static int32_t a = 0; /* Wrong */void my_func(void) { static int32_t* ptr;/* OK */ static char abc = 0;/* Wrong */}在同一行中声明所有相同类型的局部变量void my_func(void) { char a; /* OK */ char b; /* Wrong, variable with char type already exists */ char a, b; /* OK */}按顺序声明局部变量i. 自定义结构和枚举
ii. 整数类型，更宽的无符号类型优先
iii. 单/双浮点
int my_func(void) { /* 1 */ my_struct_t my; /* First custom structures */ my_struct_ptr_t* p; /* Pointers too */ /* 2 */ uint32_t a; int32_t b; uint16_t c; int16_t g; char h; /* ... */ /* 3 */ double d; float f;}总是在块的开头声明局部变量，在第一个可执行语句之前在for循环中声明计数器变量/* OK */for (size_t i = 0; i 避免在声明中使用函数调用来赋值变量，除了单个变量void a(void) { /* Avoid function calls when declaring variable */ int32_t a, b = sum(1, 2); /* Use this */ int32_t a, b; b = sum(1, 2); /* This is ok */ uint8_t a = 3, b = 4;}除了char、float或double之外，始终使用stdint.h标准库中声明的类型。例如，8位的uint8_t等不要使用stdbool.h库。分别使用1或0表示真或假/* OK */uint8_t status;status = 0;/* Wrong */#include bool status = true;永远不要与真实相比较。例如，使用if(check_func){…}替换if (check_func * 1)总是将指针与空值进行比较void* ptr;/* ... *//* OK, compare against NULL */if (ptr * NULL || ptr != NULL) {}/* Wrong */if (ptr || !ptr) {}总是使用前增量(和递减)，而不是后增量(和递减)int32_t a = 0;...a++; /* Wrong */++a; /* OK */for (size_t j = 0; j 总是使用size_t作为长度或大小变量如果函数不应该修改指针所指向的内存，则总是使用const作为指针如果不应该修改函数的形参或变量，则总是使用const/* When d could be modified, data pointed to by d could not be modified */voidmy_func(const void* d) {}/* When d and data pointed to by d both could not be modified */voidmy_func(const void* const d) {}/* Not required, it is advised */voidmy_func(const size_t len) {}/* When d should not be modified inside function, only data pointed to by d could be modified */voidmy_func(void* const d) {}当函数可以接受任何类型的指针时，总是使用void *，不要使用uint8_t *。函数在实现时必须注意正确的类型转换/* * To send data, function should not modify memory pointed to by `data` variable * thus `const` keyword is important * * To send generic data (or to write them to file) * any type may be passed for data, * thus use `void *` *//* OK example */void send_data(const void* data, size_t len) { /* OK */ /* Do not cast `void *` or `const void *` */ const uint8_t* d = data;/* Function handles proper type for internal usage */}void send_data(const void* data, int len) { /* Wrong, notnot use int */}总是使用括号和sizeof操作符不要使用变长数组。使用动态内存分配代替标准C malloc和自由函数，或者如果库/项目提供了自定义内存分配，使用它的实现看看LwMEM，一个自定义内存管理库。/* OK */#include voidmy_func(size_t size) { int32_t* arr; arr = malloc(sizeof(*arr) * n); /* OK, Allocate memory */ arr = malloc(sizeof *arr * n); /* Wrong, brackets for sizeof operator are missing */ if (arr * NULL) { /* FAIL, no memory */ } free(arr); /* Free memory after usage */}/* Wrong */voidmy_func(size_t size) { int32_t arr[size]; /* Wrong, do not use VLA */}总是将variable与0进行比较，除非它被视为布尔类型永远不要将布尔处理的变量与0或1进行比较。用NOT(!)代替size_t length = 5; /* Counter variable */uint8_t is_ok = 0; /* Boolean-treated variable */if (length) /* Wrong, length is not treated as boolean */if (length > 0) /* OK, length is treated as counter variable containing multi values, not only 0 or 1 */if (length * 0) /* OK, length is treated as counter variable containing multi values, not only 0 or 1 */if (is_ok) /* OK, variable is treated as boolean */if (!is_ok) /* OK, -||- */if (is_ok * 1) /* Wrong, never compare boolean variable against 1! */if (is_ok * 0) /* Wrong, use ! for negative check */对于注释，总是使用/* comment */，即使是单行注释在头文件中总是包含带有extern关键字的c++检查每个函数都必须包含doxygen-enabled注释，即使函数是静态的使用英文名称/文本的函数，变量，注释变量使用小写字母如果变量包含多个名称，请使用下划线。force_redraw。不要使用forceRedraw对于C标准库的包含文件，请始终使用。例如，# include 对于自定义库，请始终使用""。例如，# include“my_library.h”当转换为指针类型时，总是将星号与类型对齐，例如。uint8_t* t = (uint8_t*)var_width_diff_type始终尊重项目或库中已经使用的代码风格03 注释相关的规则不允许以//开头的注释。总是使用② comment */，即使是单行注释对于多行注释，每行使用空格+星号/* * This is multi-line comments, * written in2 lines (ok) *//** * Wrong, use double-asterisk only for doxygen documentation *//** Single line comment without space before asterisk (wrong)*//* * Single line comment in multi-line configuration (wrong) *//* Single line comment (ok) */注释时使用12个缩进(12 * 4个空格)偏移量。如果语句大于12个缩进，将注释4-空格对齐(下面的例子)到下一个可用缩进void my_func(void) { char a, b; a = call_func_returning_char_a(a); /* This is comment with 12*4 spaces indent from beginning of line */ b = call_func_returning_char_a_but_func_name_is_very_long(a); /* This is comment, aligned to 4-spaces indent */}每个可以从模块外部访问的函数都必须包含函数原型(或声明)函数名必须小写，可以用下划线_分隔。（这个原则好像因人而异）/* OK */void my_func(void);void myfunc(void);/* Wrong */void MYFunc(void);void myFunc;当函数返回指针时，将星号对齐到返回类型/* OK */const char* my_func(void);my_struct_t* my_func(int32_t a, int32_t b);/* Wrong */const char *my_func(void);my_struct_t * my_func(void);对齐所有的功能原型(使用相同/相似的功能)以提高可读性/* OK, function names aligned */void set(int32_t a);my_type_t get(void);my_ptr_t* get_ptr(void);/* Wrong */void set(int32_t a);const char * get(void);函数实现必须在单独的行中包含返回类型和可选的其他关键字/* OK */int32_tfoo(void) { return0;}/* OK */static const char*get_string(void) { return"Hello world!\r\n";}/* Wrong */int32_t foo(void) { return0;}使变量名全部小写，下划线_字符可选/* OK */int32_t a;int32_t my_var;int32_t myvar;/* Wrong */int32_t A;int32_t myVar;int32_t MYVar;按类型将局部变量分组在一起void foo(void) { int32_t a, b; /* OK */ char a; char b; /* Wrong, char type already exists */}不要在第一个可执行语句之后声明变量void foo(void) { int32_t a; a = bar; int32_t b; /* Wrong, there is already executable statement */}你可以在下一个缩进级别中声明新的变量int32_t a, b;a = foo;if (a) { int32_t c, d; /* OK, c and d are in if-statement scope */ c = foo; int32_t e; /* Wrong, there was already executable statement inside block */}用星号声明指针变量与类型对齐/* OK */char* a;/* Wrong */char *a;char * a;当声明多个指针变量时，可以使用星号对变量名进行声明/* OK */char *p, *n;结构名或枚举名必须小写，单词之间有下划线_字符结构或枚举可以包含typedef关键字所有结构成员都必须小写所有枚举成员必须是大写的结构/枚举必须遵循doxygen文档语法在声明结构体时，它可以使用以下三种不同的选项之一:1. 当结构体仅用名称声明时，它的名称后不能包含_t后缀。
struct struct_name { char* a; char b;};2. 当只使用typedef声明结构时，它的名称后面必须包含_t后缀。
typedef struct { char* a; char b;} struct_name_t;3. 当结构用name和typedef声明时，它不能包含t作为基本名称，它必须在它的名称后面包含t后缀作为typedef部分。
typedef struct struct_name { char* a; char b; char c;} struct_name_t;错误声明的例子及其建议的纠正：/* a and b must be separated to 2 lines *//* Name of structure with typedef must include _t suffix */typedef struct { int32_t a, b;} a;/* Corrected version */typedef struct { int32_t a; int32_t b;} a_t;/* Wrong name, it must not include _t suffix */struct name_t { int32_t a; int32_t b;};/* Wrong parameters, must be all uppercase */typedef enum { MY_ENUM_TESTA, my_enum_testb,} my_enum_t;在声明时初始化结构时，使用C99初始化风格/* OK */a_t a = { .a = 4, .b = 5,};/* Wrong */a_t a = {1, 2};当为函数句柄引入new typedef时，使用_fn后缀/* Function accepts 2 parameters and returns uint8_t *//* Name of typedef has `_fn` suffix */typedef uint8_t (*my_func_typedef_fn)(uint8_t p1, const char* p2);07 复合语句规则每个复合语句必须包括左花括号和右花括号，即使它只包含1个嵌套语句每个复合语句必须包含单个缩进;嵌套语句时，每个嵌套包含1个缩进大小/* OK */if (c) { do_a;} else { do_b;}/* Wrong */if (c) do_a;else do_b;/* Wrong */if (c) do_a;else do_b;在if或if-else-if语句的情况下，else必须与第一条语句的右括号在同一行/* OK */if (a) {} elseif (b) {} else {}/* Wrong */if (a) {}else {}/* Wrong */if (a) {}else{}在do-while语句的情况下，while部分必须与do部分的右括号在同一行/* OK */do { int32_t a; a = do_a; do_b(a);} while (check);/* Wrong */do{/* ... */} while (check);/* Wrong */do {/* ... */}while (check);每一个开括号都需要缩进if (a) { do_a;} else { do_b; if (c) { do_c; }}不要做没有花括号的复合语句，即使是单个语句。下面的例子展示了一些不好的做法if (a) do_b;else do_c;if (a) do_a; else do_b;空while循环、do-while循环或for循环必须包含花括号/* OK */while (is_register_bit_set) {}/* Wrong */while (is_register_bit_set);while (is_register_bit_set) { }while (is_register_bit_set) {}如果while(或for、do-while等)为空(嵌入式编程中也可能是这种情况)，请使用空的单行括号/* Wait for bit to be set in embedded hardware unituint32_t* addr = HW_PERIPH_REGISTER_ADDR;/* Wait bit 13 to be ready */while (*addr & (1 尽量避免在循环块内递增变量，参见示例/* Not recommended */int32_t a = 0;while (a 08 分支语句规则为每个case语句添加单个缩进使用额外的单缩进break语句在每个case或default/* OK, every case has single indent *//* OK, every break has additional indent */switch (check) { case 0: do_a; break; case 1: do_b; break; default: break;}/* Wrong, case indent missing */switch (check) {case 0: do_a; break;case 1: do_b; break;default: break;}/* Wrong */switch (check) { case 0: do_a; break; /* Wrong, break must have indent as it is under case */ case 1: do_b; /* Wrong, indent under case is missing */ break; default: break;}总是包含default语句/* OK */switch (var) { case 0: do_job; break; default: break;}/* Wrong, default is missing */switch (var) { case 0: do_job; break;}如果需要局部变量，则使用花括号并在里面放入break语句。将左花括号放在case语句的同一行switch (a) { /* OK */ case 0: { int32_t a, b; char c; a = 5; /* ... */ break; } /* Wrong */ case 1: { int32_t a; break; } /* Wrong, break shall be inside */ case 2: { int32_t a; } break;}09 宏和预处理指令总是使用宏而不是文字常量，特别是对于数字所有的宏必须是全大写的，并带有下划线_字符(可选)，除非它们被明确标记为function，将来可能会被常规函数语法替换/* OK */#define MY_MACRO(x) ((x) * (x))/* Wrong */#define square(x) ((x) * (x))总是用圆括号保护输入参数/* OK */#define MIN(x, y) ((x) 总是用括号保护最终的宏计算/* Wrong */#define MIN(x, y) (x) 当宏使用多个语句时，使用do-while(0)语句保护它typedef struct { int32_t px, py;} point_t;point_t p; /* Define new point *//* Wrong implementation *//* Define macro to set point */#define SET_POINT(p, x, y) (p)->px = (x); (p)->py = (y) /* 2 statements. Last one should not implement semicolon */SET_POINT(&p, 3, 4); /* Set point to position 3, 4. This evaluates to... */(&p)->px = (3); (&p)->py = (4); /* ... to this. In this example this isnot a problem. *//* Consider this ugly code, however it is valid by C standard (not recommended) */if (a) /* If a is true */ if (b) /* If b is true */ SET_POINT(&p, 3, 4);/* Set point to x = 3, y = 4 */ else SET_POINT(&p, 5, 6);/* Set point to x = 5, y = 6 *//* Evaluates to code below. Do you see the problem? */if (a) if (b) (&p)->px = (3); (&p)->py = (4); else (&p)->px = (5); (&p)->py = (6);/* Or if we rewrite it a little */if (a) if (b) (&p)->px = (3); (&p)->py = (4); else (&p)->px = (5); (&p)->py = (6);/* * Ask yourself a question: To which `if` statement `else` keyword belongs? * * Based on first part of code, answer is straight-forward. To inner `if` statement when we check `b` condition * Actual answer: Compilation error as `else` belongs nowhere *//* Better and correct implementation of macro */#define SET_POINT(p, x, y) do { (p)->px = (x); (p)->py = (y); } while (0) /* 2 statements. No semicolon after while loop *//* Or even better */#define SET_POINT(p, x, y) do { \ /* Backslash indicates statement continues in new line */ (p)->px = (x); \ (p)->py = (y); \} while (0) /* 2 statements. No semicolon after while loop *//* Now original code evaluates to */if (a) if (b) do { (&p)->px = (3); (&p)->py = (4); } while (0); else do { (&p)->px = (5); (&p)->py = (6); } while (0);/* Every part of `if` or `else` contains only `1` inner statement (do-while), hence this is valid evaluation *//* To make code perfect, use brackets for every if-ifelse-else statements */if (a) { /* If a is true */ if (b) { /* If b is true */ SET_POINT(&p, 3, 4);/* Set point to x = 3, y = 4 */ } else { SET_POINT(&p, 5, 6);/* Set point to x = 5, y = 6 */ }}不缩进子语句内#if语句/* OK */#if defined(XYZ)#if defined(ABC)/* do when ABC defined */#endif /* defined(ABC) */#else /* defined(XYZ) *//* Do when XYZ not defined */#endif /* !defined(XYZ) *//* Wrong */#if defined(XYZ) #if defined(ABC) /* do when ABC defined */ #endif /* defined(ABC) */#else /* defined(XYZ) */ /* Do when XYZ not defined */#endif /* !defined(XYZ) */文档文档化的代码允许doxygen解析和通用的html/pdf/latex输出，因此正确地执行是非常重要的。对变量、函数和结构/枚举使用doxygen支持的文档样式经常使用\作为doxygen，不要使用@始终使用5x4空格(5个制表符)作为文本行开始的偏移量/** * \brief Holds pointer to first entry in linked list * Beginning of this text is 5 tabs (20 spaces) from beginning of line */statictype_t* list;每个结构/枚举成员都必须包含文档注释的开头使用12x4空格偏移量/** * \brief This is point struct * \note This structure is used to calculate all point * related stuff */typedef struct { int32_t x; /*!函数的文档必须在函数实现中编写(通常是源文件)函数必须包括简要和所有参数文档如果每个参数分别为in或out输入和输出，则必须注意如果函数返回某个值，则必须包含返回形参。这不适用于void函数函数可以包含其他doxygen关键字，如note或warning在参数名和描述之间使用冒号:/** * \brief Sum `2` numbers * \param[in] a: First number * \param[in] b: Second number * \return Sum of input values */int32_tsum(int32_t a, int32_t b) { return a + b;}/** * \brief Sum `2` numbers and write it to pointer * \note This function does notreturn value, it stores it to pointer instead * \param[in] a: First number * \param[in] b: Second number * \param[out] result: Output variable used to save result */voidvoid_sum(int32_t a, int32_t b, int32_t* result) { *result = a + b;}如果函数返回枚举的成员，则使用ref关键字指定哪个成员/** * \brief My enumeration */typedef enum { MY_ERR, /*!对常量或数字使用符号(' NULL ' => NULL)/** * \brief Get data from input array * \param[in] in: Input data * \return Pointer to output data on success, `NULL` otherwise */const void *get_data(const void* in) { return in;}宏的文档必须包括hideinitializer doxygen命令/** * \brief Get minimal value between `x` and `y` * \param[in] x: First value * \param[in] y: Second value * \return Minimal value between `x` and `y` * \hideinitializer */#define MIN(x, y) ((x) 10 头/源文件在文件末尾留下一个空行每个文件都必须包括文件的doxygen注释和后跟空行的简要描述(使用doxygen时)/** * \file template.h * \brief Template include file */ /* Here is empty line */每个文件(头文件或源文件)必须包含许可证(开始注释包括单个星号，因为doxygen必须忽略这个)使用与项目/库已经使用的相同的许可证/** * \file template.h * \brief Template include file *//* * Copyright (c) year FirstName LASTNAME * * Permission is hereby granted, free of charge, to any person * obtaining a copy of this software and associated documentation * files (the "Software"), to deal in the Software without restriction, * including without limitation the rights to use, copy, modify, merge, * publish, distribute, sublicense, and/or sell copies of the Software, * and to permit persons to whom the Software is furnished to do so, * subject to the following conditions: * * The above copyright notice and this permission notice shall be * included in all copies or substantial portions of the Software. * * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, * EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES * OF MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE * AND NONINFRINGEMENT. IN NO EVENT SHALL THE AUTHORS OR COPYRIGHT * HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY, * WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING * FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR * OTHER DEALINGS IN THE SOFTWARE. * * This file is part of library_name. * * Author: FirstName LASTNAME */头文件必须包含保护符#ifndef头文件必须包含c++检查在c++检查之外包含外部头文件首先用STL C文件包含外部头文件，然后是应用程序自定义文件头文件必须包含其他所有头文件，以便正确编译，但不能包含更多头文件(如果需要，.c应该包含其余的头文件)头文件必须只公开模块公共变量/类型/函数在头文件中使用extern作为全局模块变量，稍后在源文件中定义它们/* file.h ... */#ifndef ...extern int32_t my_variable; /* This is global variable declaration in header */#endif/* file.c ... */int32_t my_variable; /* Actually defined in source */不要把.c文件包含在另一个.c文件中.c文件应该首先包含相应的.h文件，然后是其他文件，除非另有明确的必要在头文件中不包含模块私有声明头文件示例(示例中没有license)/* License comes here */#ifndef TEMPLATE_HDR_H#define TEMPLATE_HDR_H/* Include headers */#ifdef __cplusplusextern "C" {#endif /* __cplusplus *//* File content here */#ifdef __cplusplus}#endif /* __cplusplus */#endif /* TEMPLATE_HDR_H */以上就是今天分享的文章，老外的编程风格看起来很熟悉，比如ST官方的驱动库，大家可以参考一下。
来源：玩转嵌入式